ST. LOUIS - Two-time defending national champion Johnny Weir put his signature on the U.S. Championships, donning a swan costume — including a red glove to signify a beak —and skated the only clean program among the top five to take a commanding lead for a third straight title and one of three slots on the 2006 Olympic team. “I’m just very, very elated right now,” Weir said Thursday. Michael Weiss, 29 and skating in his 13th nationals, landed on two feet instead of one on a planned quadruple jump but is in second place. Long-limbed Evan Lysacek, 20, looking stunned after he fell during a benign step sequence, is in third. In the ladies short program, Sasha Cohen, four-time national runner-up and favored in the absence of an injured Michelle Kwan, skated a near-flawless routine to lead. Emily Hughes, sister of 2002 gold medalist Sarah, was second and Bebe Liang, the final skater of the night, made a surprise move into third going into Saturday’s free skate. Kimmie Meissner is fourth. Finishing third could be perilous. Kwan has filed an injury waiver that would allow her to be named to the Olympic team without skating here. If a committee grants it, it would likely bump the bronze medalist. National champions get automatic Olympic berths. A decision will be made on Kwan and the remaining men’s and ladies’ slots after the competition concludes Saturday. On Thursday, Cohen landed all her jumps, including two triples, and appeared to skate aggressively despite the lingering effects of a flu that, she said, kept her bedridden most of the past five days. “This is definitely not half as good as I’ve been doing in practice” she said. Men’s 2002 Olympic bronze medalist Tim Goebel, who has said he’ll retire after this season, is fifth, behind Matt Savoie. Goebel, the 2005 national silver medalist, touched his hand to the ice on a quadruple and landed unsteadily on his triple axel. Broadmoor Skating Club’s Ryan Bradley, 22, of Colorado Springs is in sixth place. Weir, skating to Camille Saint-Saens’ “The Swan,” has taken the role to heart — and to fabric. His specially made costume is a prop to a graceful program that included no quads but a triple axel and triple-lutz/triple toe combination. It ended with Weir fluttering his arms gracefully, like . . . a swan. “When I’ve skated poorly in this, I blame my glove,” Weir said, adding he named the costume “Camille” in the composer’s honor. The fluid Weir drew an enthusiastic response from the audience as did Bradley, the only other skater in the field to skate clean. Bradley’s program was high on success but relatively low-risk, which is why he didn’t place higher. Still, “it’s such a rush,” he said of his return to nationals after a broken arm kept him away last year. Weir heard cheers for his program too but noted the difference in a description that was purely Weir. “The music is very lyrical,” Weir said. “It’s not one of those ones you can clap along to. I watched Ryan Bradley skate earlier with ‘Zorba’ and it’s a different kind of support. This one they kind of sat back and had their cognac and their cigarettes and they’re just relaxing and watching. His was more like a vodka-shot, let’s-snort-coke kind of experience.” Then, Weir apologized. But not for the swan suit. “Sorry about the drug references,” he said.